Internal combustion engine heads are typically constructed using a casting process. In engines containing multiple valves per cylinder, relatively complex passageways through the head casting may be formed to provide proper component clearances, lubrication and control. As additional valves and hydraulically controlled devices are added to the head, casting cores used to create the head become more complex and may be more likely to break during the casting process. The result of core breakage may include scrapping the castings or performing substantial machining operations that are not typically part of the production process.
Furthermore, some casting designs include blind bores which may allow air pockets to be formed within hydraulic passages of the head. The bores may also house machining chips which may not be easily flushed out during cylinder head cleaning.